Progress 06/01/24 to 05/31/25
Outputs Target Audience:The target audience for the products of this project includes: 1. Researchers in food science, nutrition, cardiovascular disease, gut microbiome, and plant genetics 2. Government scientists and policymakers 3. Dietitians and clinicians working in the area of diet and cardiovascular disease 4. Blueberry breeders 5. Blueberry growers and distributors 6. Blueberry consumers Changes/Problems:The major challenge we have encountered was in regards to Aim 2. Specifically, the sugar in blueberry pulp is incompatible with our anaerobic fecal femrentation method and choline conversion to TMA assay. Therefore, we have opted to use phenolic-rich blueberry skin, which contain the majority of the compound of interest (chlorogenic acid). This limits us to assessing the activity of compounds contains in skins, but phenolics are generally concentrated in skins anyway in blueberries and other fruits. What opportunities for training and professional development has the project provided?The PhD students (A McAmis) and postdotoral scholar (A Din)who worked on this project learned valuable skills relevant to working in the fruit industry (berry genotypes and composition), as well as analytical skills (beryy and fermenta analysis by UPLC-MS/MS), anaerobic microbiology and fermentation, aniumal husbandry, animal models of pharmacokinetics, and biochemistryand writing/communication (publishing and presenting). How have the results been disseminated to communities of interest?We have published 1 paper in a peer-reviewed journal, submitted another for publication in a perr-reviewed journal, and submitted 2 abstracts for conferences (1 national, 1 international). What do you plan to do during the next reporting period to accomplish the goals?We will focus on the remaining experiments, primarily in Objectives 1 and 3 Objective 1. Determine if blueberry CGA predicts inhibition of TMAO formation and atherosclerosis when cultivars with >10-fold difference in CGA are administered to rodents. Hypothesis and Approach: We will use rodent models to test the impact of blueberry cultivars with different CGA content on TMA/TMAO production acutely and chronically (Exp. 1-A-B rats) and on atherosclerosis development (Exp. 2, ApoE−/− mice). We hypothesize that 1) blueberry supplementation will reduce TMAO and prevent atherosclerosis, and 2) CGA-rich blueberries will be more effective than CGA-poor blueberries. Experiment 1. Compare efficacy of CGA-rich and CGA-poor blueberries for inhibiting TMA and TMAO production in vivo. We will perform both acute and chronic experiments, enabling us to probe distinct mechanisms: direct TMA lyase inhibition in acute experiments (Exp.1A) vs. altered microbiome composition, cutC/D copy numbers and FMO3 expression (not inhibition) in chronic experiments (Exp. 1B). Identifying mechanism(s) of action is critical for the subsequent design of optimal dietary strategies to maximize the effects of blueberry consumption. Exp. 1A: Acute Effects. We will first compare the acute efficacy of CGA-rich vs. CGA-poor blueberries to reduce TMA and TMAO. We will employ a randomized crossover design to compare the acute efficacy of CGA-rich or CGA-poor blueberry powders and pure CGA matched to CGA content of blueberry powders. We hypothesize that blueberries and CGA will lower TMA and TMAO in vivo, and that higher doses of CGA) will result in greater inhibition. Exp. 1B: Chronic Effects. Chronic CGA supplementation improves the gut microbiome and protects against CVD in animal models. CGA-rich blueberries may reduce TMA and TMAO by mechanisms requiring chronic exposure, including shifts in microbiome taxonomic distribution, altered levels of cutC/D, and/or changes to FMO3 expression. We will perform a chronic supplementation study to assess these mechanisms. We hypothesize that chronic consumption of blueberries and CGA will reduce TMA and TMAO in a dose-dependent manner. Experiment 2. Determine whether the CGA content of blueberries affects their ability to prevent or delayatherosclerosis in choline-fed ApoE-/- mice. We hypothesize that blueberries will prevent development of atherosclerosis in choline-fed ApoE-/- mice concurrent with suppressing TMAO, and that CGA-rich blueberries will be more effective than CGA-poor blueberries at both. We will determine whether blueberries inhibit atherosclerosis and reduce TMAO levels in anestablished atherosclerosis model (ApoE-/- mice) fed 1% choline. Objective 3: Elucidate mechanism(s) by which CGA and CGA-rich blueberries modulate TMA formation in the gut using isolated bacteria known to carry cutC/D Hypothesis and Approach: We will interrogate bacterial mechanisms underlying the TMA-lowering effects of CGA-rich blueberries by performing fermentations with bacterial genera known to carry the cutC/D gene cluster. We hypothesize that CGA-rich blueberries directly inhibit TMA lyase or reduce cutC copy numbers or viability of bacterial species carrying cutC. We also hypothesize that CGA content of berries is directly correlated to activity. Experiment 4. Evaluate mechanisms by which CGA-rich blueberries inhibit bacterial TMA production. We will assess the potential for blueberries, pure CGA, phenolic extracts, etc. to directly inhibit choline TMA lyase. Direct inhibition requires that the inhibitory molecule(s), substrate, and enzyme be simultaneously present. Exp. 4A. Isolated live bacterial fermentations. We will assess the potential for blueberry cultivars to inhibit TMA lyase. We will perform fermentations with gut bacterial strains that carry cutC/D. We hypothesize that inhibitory effects of CGA and blueberries in fecal slurries will be reproduced with isolated bacterial strains, and that TMA lyase inhibition and/or or growth inhibition of TMA producers are mechanisms of action of CGA-rich blueberries. Exp. 4B. TMA lyase inhibitory experiments in lysed (non-viable) bacteria. A limitation to assessing enzyme activity in live cells is that alterations to growth, metabolic activity, viability, or community composition may confound direct enzyme inhibition. To overcome this, we will assay TMA lyase inhibition in non-viable cell lysates from isolated bacteria used above. We will prepare lysates to obtain cell-free TMA lyase, screen lysates to confirm TMA lyase activity, and then perform inhibitory assays with blueberry cultivar or CGA digestas as described above. Effects in lysed (non-viable) cells are due to TMA lyase inhibition and not altered bacterial viability, growth, cutC/D numbers or expression.?
Impacts What was accomplished under these goals?
In the present project period (Year 1 of the project), we conducted Experiment 3A-B(Objective 2). Objective 2. Determine whether blueberry chlorogenic acid (CGA) content correlates with inhibition of choline conversion to TMA in multipleaccessions from a genetic diversity population with a large spread of CGA in our validated ex vivo-in vitro human fecalfermentation model. Hypothesis and Approach: Weperformedfecal fermentations to build on our preliminaryin vitrodata that CGA-richblueberries inhibit the microbial generation of TMAand establish whether blueberry CGA content exerts adose-dependent effect. We hypothesized that CGA content will strongly correlate with reduced TMA production by gut bacteria. Experiment 3. Screen blueberry cultivars with large variation in CGA content for inhibition of choline-d9conversion toTMA-d9by human fecal bacteria. We will perform fermentations per our methods to assess the inhibition of choline-d9conversion to TMA-d9by human fecal bacteria. Feces from healthy donors will be obtained from OpenBiome (Cambridge, MA). Exp. 3A: Blueberry Fermentations. To identify the role of CGA for reducing TMA production, westudied20 blueberrycultivars fromgenetic diversity populations with a wide range of CGA levels. Wesubjected blueberries tosimulated oral, gastric and small intestinalin vitrodigestion by our established protocols (equiv. to 0.5-1 servings/2 L upper GIvolume) and then fermentedthem with choline-d9substrate to compare efficacy for inhibiting TMA-d9production vs. blank digestaand each other. We hypothesized that blueberry CGA levels correlate to inhibition of TMA production. Weperformed linearregression analyses using CGA content (independent variable) and TMA inhibition outcomes such final TMA levels, AUCs, %TMA inhibition vs control, etc. (dependent variables). Exp. 3B: Berry Component Fermentations. Weisolatedthe effects of CGA and other phenolics vs. non-phenolic blueberrycomponents by preparing CGA/phenolic-rich extracts from blueberries and fermenting these extracts vs. the unextractedmaterial (polysaccharides, proteins, lipids, etc.). Wedigested and fermented the phenolic extract and unextracted material separately and compared them to each other and whole digesta to identify effects of phenolics vs. other material (fiber, etc.).Similar analyses wereperformed to those for Exp. 3A. Findings: CGA levels in whole berries ranged from 2.6-146 mg/100 g fresh weight (FW), while CGA concentrations in blueberry skins ranged from 0.14-9.7 mg/g. No significant differences were observed in TMA-d9production among the 4 highest and 4 lowest CGA genotypes in kinetic curves or area under the curve (AUC) values. However, significant differences were observed between all genotypes compared to controls, with ~19.4.% reduction in TMA-d9AUCs compared to blank digesta, indicating that phenolic-rich skin provides similar TMA-lowering benefits across blueberry varieties. This suggests that the CGA content of genotypes is not a crucial factor for lowering TMA. Preliminary evidence suggests that fiber is also not the primary driver of the inhibitory activities of blueberry skins. Future studies, including rodent and human studies, are needed to confirm thisin vitrostudy and understand why blueberries may inhibit TMA and potentially TMAO, asin vitrostudies have limitations, and the mechanism of TMA reduction remains unclear. We also conducted preliminary experiments towards Experiment 1 (Objective 1). Objective 1. Determine if blueberry CGA predicts inhibition of TMAO formation and atherosclerosis when cultivars with >10-fold difference in CGA are administered to rodents. Hypothesis and Approach: We will use rodent models to test the impact of blueberry cultivars with different CGA content on TMA/TMAO production acutely and chronically (Exp. 1-A-B rats) and on atherosclerosis development (Exp. 2, ApoE−/− mice). We hypothesize that 1) blueberry supplementation will reduce TMAO and prevent atherosclerosis, and 2) CGA-rich blueberries will be more effective than CGA-poor blueberries. Experiment 1. Compare efficacy of CGA-rich and CGA-poor blueberries for inhibiting TMA and TMAO production in vivo. We will perform both acute and chronic experiments, enabling us to probe distinct mechanisms: direct TMA lyase inhibition in acute experiments (Exp.1A) vs. altered microbiome composition, cutC/D copy numbers and FMO3 expression (not inhibition) in chronic experiments (Exp. 1B). Identifying mechanism(s) of action is critical for the subsequent design of optimal dietary strategies to maximize the effects of blueberry consumption While dietary modifications regulate TMAO production, the impact of different intake methods, including oral gavage, dietary supplementation, and conditions such as fasting versus non-fasting, has not been fully explored. We conducted preliminary experiments to identify optimal rat experimental doses of choline to study inhibition of TMAO formation Twelve female Sprague-Dawley rats were divided into three diet groups (n = 4 per group): no-choline (0% choline), low-choline (0.08% choline), and high-choline (1% choline). Choline and TMAO fasting and non-fasting blood concentrations, and their kinetics following an acute choline challenge, were assessed before and after a 2-week dietary intervention with the distinct choline dietary levels. Fasting choline was under tight control, with little effect of dietary choline. Non-fasting choline was more variable, with high dietary choline reflected in higher blood choline. Greater levels of dietary choline were reflected in significantly greater levels of TMAO, particularly for non-fasting levels. Kinetic profiling demonstrated additional information regarding the appearance and clearance of these compounds from blood. These results suggest that acute oral choline gavage is likely most suitable for studies targeting acute (direct) inhibitors, whereas a choline-rich diet with assessment of fasting and non-fasting blood levels is more suitable for studying alterations to TMAO production capacity. Future research should examine the impact on atherosclerosis biomarkers and microbiome diversity to deepen the understanding of TMAO regulation and its cardiovascular implications.
Publications
- Type:
Peer Reviewed Journal Articles
Status:
Published
Year Published:
2025
Citation:
Din A, MG Sweet, AM McAmis, JG Ratliff, AB Pon Velayutham, AP Neilson, Establishing reliable blood biomarkers for trimethylamine N-oxide status in rodents: effects of oral choline challenge, dietary choline and fasting conditions. J Nutr Biochem 2025, 141:109905. Preprint DOI: 10.1101/2024.12.06.627229. DOI: 10.1016/j.jnutbio.2025.109905. PMID: 40120776.
- Type:
Peer Reviewed Journal Articles
Status:
Under Review
Year Published:
2025
Citation:
McAmis AM, MG Sweet, S Chadwick-Corbin, JG Ratliff, MF Mengist, NV Bassil, PV Anandh Babu, M Iorizzo, AP Neilson, Inhibition of pro-atherogenic trimethylamine production by human gut bacteria is not determined by varying chlorogenic acid content in highbush blueberries, Submitted, Food Funct TBD, 2025. Manuscript ID: FO-ART-06-2025-002676. Preprint DOI: 10.1101/2025.06.20.660815.
- Type:
Conference Papers and Presentations
Status:
Submitted
Year Published:
2025
Citation:
Din A, MG Sweet, AM McAmis, JG Ratliff , AP Neilson, Chlorogenic acid inhibits microbial trimethylamine formation in a defined Proteus mirabilis fermentation model, poster presented at the 13th Prebiotics & - Rome Congress 2023, Rome, Italy, 14-16 Sept 2025
- Type:
Conference Papers and Presentations
Status:
Submitted
Year Published:
2025
Citation:
McAmis AM, MG Sweet, S Chadwick-Corbin, JG Ratliff, NV Bassil, PV Anandh Babu, Massimo Iorizzo, AP Neilson, Inhibition of trimethylamine production in vitro does not differ in blueberries with varying chlorogenic acid content. Poster presented at the 10th Biennial Berry Health Benefits Symposium (BHBS), 7-9 Oct 2025, Philadelphia, PA.
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